Bad cat?

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DallasTahoe

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98 Yukon 4wd, keep getting code p0430, says catalyst system below efficiency threshold bank 2. Would that be the catalytic converter? I replaced all the o2 sensors a couple years ago just as basic maintenance. Thoughts?


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exp500

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We are gonna need more Info... Like what engine, mileage, prior exhaust work....
so the answer is "could be". If it is only throwing codes and runs perfect then try new O2 sensors.
 
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DallasTahoe

DallasTahoe

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We are gonna need more Info... Like what engine, mileage, prior exhaust work....
so the answer is "could be". If it is only throwing codes and runs perfect then try new O2 sensors.
5.7, single flow master 40. New heads 3 years ago, Doesn’t smoke, runs smooth from idle on up. It’s only throwing p0430, no misfiring, no rotten egg smell. I’ve cleared the code a couple of times, just to see how long it takes to come on. Right around 5 miles or 2 key strokes. If it’s a short trip


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exp500

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Can you tell by your scantool the voltages? F/R sensors? Usually the rear sensor, but the difference and time is what sets code. Some have had success using an adapter adding about 1/2 in length to the port. Cheap fix.
 
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DallasTahoe

DallasTahoe

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Can you tell by your scantool the voltages? F/R sensors? Usually the rear sensor, but the difference and time is what sets code. Some have had success using an adapter adding about 1/2 in length to the port. Cheap fix.
I swapped the downstream sensors and now no check engine light, I did notice one of them was shorter than the other, the short one is now on bank two and working fine now [emoji2375]


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exp500

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Please edit your original post title, add "SOLVED". Thanks.
 
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DallasTahoe

DallasTahoe

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Please edit your original post title, add "SOLVED". Thanks.
Well I can’t, it came back today, I don’t drive it much, mainly on the weekends. Atleast I can rule out the o2 sensor, I’ll pull the plugs tomorrow and check those


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exp500

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If it's been a couple years, change Dist cap. United DCR820X or Delco.
 
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DallasTahoe

DallasTahoe

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Can you tell by your scantool the voltages? F/R sensors? Usually the rear sensor, but the difference and time is what sets code. Some have had success using an adapter adding about 1/2 in length to the port. Cheap fix.
I can’t post a video but when I had it on my scanner the downstream sensors were bouncing up and down, but on the bank 2 downstream it wasnt moving as much as bank 1, keep in mind that’s the sensor that was on bank 1, so I’m thinking it is the cat


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exp500

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They shouldn't bounce, more like a wave if charted. Replug connectors, Ohm check Sensors, Check wires for wear thru or Pinch spots. Might just be bad O2's. Heater circuit is troublesome, may need to wring out the harness. If cats were gone you likely would have performance issues/missfires.
 

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